Male development in higher plants is a complex process which requires the correct spatial and temporal expression of a large number of male fertility genes. They include the genes required for the structure of the male organs, as well as genes required for male gamete development. Male-sterile mutants, impaired in male fertility functions, have helped to identify a number of these genes in various plant species including Arabidopsis thaliana, the model crucifer. In A. thaliana, once these genes are mapped, they can be cloned by chromosome walking. Alternative strategies of cloning will be facilitated by the isolation of similar mutants by tagging with transposable elements, T-DNA, or by mutagen-induced deletion. Once the genes required for male fertility are cloned and their wild type function identified, an understanding of the molecular basis of male fertility is likely to result. The combination of genetic dissection and the modern techniques of genome manipulation have made such a goal feasible.